: : I am wondering if anyone out there has atempted to implement a Graphic EQ, like the one in WinAMP, with the coloured bars?: : : : Thnx in advance.: : : It is called a "Audio Spectrum Analyzer" that uses Fast Fourier Transforms.....email me and I will point you in the right direction.: : : Could You please point me to the right direction too?

: : : I am wondering if anyone out there has atempted to implement a Graphic EQ, like the one in WinAMP, with the coloured bars?: : : : : : Thnx in advance.: : : : : : It is called a "Audio Spectrum Analyzer" that uses Fast Fourier Transforms.....email me and I will point you in the right direction.: : : : : : Could You please point me to the right direction too?: : :

hey? where is everyone going? "Audio Spectrum Analyzer" is not a Graphic Equalizer!!! the first displays the Dancing Bars. the other is a DSP.

1 Implement a set of hi/lowpass-filters. These split the signal in 2: a part with the higher tones, and a part with the lower tones. If you want a 5-band EQlike on 50, 200, 800, 3200 & 12800 Hz, you implement a filter on 6400 Hz (log-center of 3200 & 12800), boost the upper part with the level for 12800 Hz, and send the lower part to a 1600 Hz filter, boost the upper part,...

This technique is pretty fast (if you use the right filters) but the noise-level gets boosted every stage.

2 Implement a set of bandpassfilters, 1 low- & 1 highpassfilter. Apply them on the source signal if they are active (Gain != 0db)

This technique is also reasonable fast, the noise-level stays low, but the filters are hard to implement since they do not fit each other automatically.

3 You could do an FFT & IFFT: Dont ! This is slow and not easy to implement.

: I am wondering if anyone out there has atempted to implement a Graphic EQ, like the one in WinAMP, with the coloured bars?: : Thnx in advance.: : :

: There are 2 ways to make a graphic EQ: : 1 Implement a set of hi/lowpass-filters. These split the signal in 2: a part with the higher tones, and a part with the lower tones. If you want a 5-band EQlike on 50, 200, 800, 3200 & 12800 Hz, you implement a filter on 6400 Hz (log-center of 3200 & 12800), boost the upper part with the level for 12800 Hz, and send the lower part to a 1600 Hz filter, boost the upper part,...: : This technique is pretty fast (if you use the right filters) but the noise-level gets boosted every stage.: : 2 Implement a set of bandpassfilters, 1 low- & 1 highpassfilter. Apply them on the source signal if they are active (Gain != 0db): : This technique is also reasonable fast, the noise-level stays low, but the filters are hard to implement since they do not fit each other automatically.: : 3 You could do an FFT & IFFT: Dont ! This is slow and not easy to implement.: : : I am wondering if anyone out there has atempted to implement a Graphic EQ, like the one in WinAMP, with the coloured bars?: : : : Thnx in advance.: : : : : : : : Yes I am trying to implement one using FFT & IFFT in Visual Basic!!!

2 FFT is SLOW because it calculates too much unnecesseary frequency-amplitudes. Our ear hears frequencies in a logaritmic order: eg. we experience 100Hz & 200 Hz as the same distance between 200 Hz & 400 Hz. If you use FFT with base-frequency of lets say 100 Hz, you get 100, 200, 300, 400, ... up till 22100 Hz. Result: bad resolution in the low registers & too much information for the highest tones. Solution for the lower frequencies: increase the block-size. But: then the latency increases & the calculation-time gets longer & the resolution for the higher frequencies gets even bigger. So this is no solution at all for any adio-related application !

So: you could use it because you found a FFT-library on the web and want to check it out, but if you get serious about audio...